U.S. patent application number 16/329658 was filed with the patent office on 2019-06-27 for quality control of high performance superconductor tapes.
The applicant listed for this patent is University of Houston System. Invention is credited to Goran Majkic, Venkat Selvamanickam.
Application Number | 20190198745 16/329658 |
Document ID | / |
Family ID | 61301449 |
Filed Date | 2019-06-27 |
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United States Patent
Application |
20190198745 |
Kind Code |
A1 |
Majkic; Goran ; et
al. |
June 27, 2019 |
Quality Control of High Performance Superconductor Tapes
Abstract
A superconductor tape and method for manufacturing, measuring,
monitoring, and controlling same are disclosed. Embodiments are
directed to a superconductor tape which includes a superconductor
film overlying a buffer layer which overlies a substrate. In one
embodiment, the superconductor film is defined as having a c-axis
lattice constant higher than 11.74 Angstroms. In another
embodiment, the superconductor film comprises BaMO.sub.3, where
M=Zr, Sn, Ta, Nb, Hf, or Ce, and which has a (101) peak of
BaMO.sub.3 elongated along an axis that is between 60.degree. to
90.degree. from an axis of the (001) peaks of the superconductor
film. These and other embodiments achieve well-aligned nanocolumnar
defects and thus a high lift factor, which can result in superior
critical current performance of the tape in, for example, high
magnetic fields.
Inventors: |
Majkic; Goran; (Houston,
TX) ; Selvamanickam; Venkat; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
University of Houston System |
Houston |
TX |
US |
|
|
Family ID: |
61301449 |
Appl. No.: |
16/329658 |
Filed: |
August 29, 2017 |
PCT Filed: |
August 29, 2017 |
PCT NO: |
PCT/US2017/049087 |
371 Date: |
February 28, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62381369 |
Aug 30, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 39/225 20130101;
H01L 39/126 20130101; H01L 39/2422 20130101; H01L 39/143 20130101;
H01L 39/2441 20130101; Y02E 40/60 20130101; Y02E 40/64 20130101;
H01L 39/2461 20130101 |
International
Class: |
H01L 39/24 20060101
H01L039/24; H01L 39/12 20060101 H01L039/12; H01L 39/14 20060101
H01L039/14 |
Goverment Interests
GOVERNMENT SPONSORSHIP:
[0002] Office of Naval Research Award N00014-14-1-0182.
Claims
1. A superconductor tape comprising: a substrate; a buffer layer
overlying the substrate; and a superconductor film overlying the
buffer layer; wherein the superconductor film is defined as having
a c-axis lattice constant higher than 11.74 Angstroms.
2. The superconductor tape of claim 1, wherein the superconductor
film is over 10 meters in length.
3. The superconductor tape of claim 1, wherein the superconductor
film comprises 5 to 30 mol % of dopant selected from the group
consisting of Zr, Sn, Ta, Nb, Hf, Ce, and a combination
thereof.
4. The superconductor tape of claim 1, wherein the superconductor
film comprises BaMO.sub.3, where M=Zr, Sn, Ta, Nb, Hf, or Ce, and
which has a (101) peak of BaMO.sub.3 elongated along an axis that
is between 60.degree. to 90.degree. from an axis of the (001) peaks
of the superconductor film.
5. A superconductor tape comprising: a substrate; a buffer layer
overlying the substrate; and a superconductor film overlying the
buffer layer; wherein the superconductor film comprises BaMO.sub.3,
where M=Zr, Sn, Ta, Nb, Hf, or Ce, and which has a (101) peak of
BaMO.sub.3 elongated along an axis that is between 60.degree. to
90.degree. from an axis of the (001) peaks of the superconductor
film.
6. The superconductor tape of claim 5, wherein the (101) peak of
BaMO.sub.3 is measured by X-ray diffraction.
7. The superconductor tape of claim 5, wherein the superconductor
film is over 10 meters in length.
8. The superconductor tape of any of the above claims claim 5,
wherein the superconductor film comprises 5 to 30 mol % of dopant
selected from the group consisting of Zr, Sn, Ta, Nb, Hf, Ce, and a
combination thereof.
9. The superconductor tape of any of the above claims claim 5,
wherein the superconductor film is defined as having a c-axis
lattice constant higher than 11.74 Angstroms.
10. A superconductor tape comprising: a substrate; a buffer layer
overlying the substrate; and a superconductor film overlying the
buffer layer; wherein the superconductor film comprises BaMO.sub.3,
where M=Zr, Sn, Ta, Nb, Hf, or Ce, and which has a (101) peak of
BaMO.sub.3 located at a 2theta angle higher than 30.degree. when
measured by X-ray Diffraction using copper k alpha radiation.
11. The superconductor tape of claim 10, wherein the superconductor
film comprises 5 to 30 mol % of dopant selected from the group
consisting of Zr, Sn, Ta, Nb, Hf, Ce, and a combination
thereof.
12. The superconductor tape of claim 10, wherein the superconductor
film is defined as having a c-axis lattice constant higher than
11.74 Angstroms.
13-21. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATION(s)
[0001] This application claims priority to U.S. provisional patent
application number 62/381,369, filed on Aug. 30, 2016, which is
hereby incorporated herein by reference in its entirety.
FIELD OF THE DISCLOSURE
[0003] The embodiments disclosed herein are in the field of
superconductor tapes. More particularly, the embodiments disclosed
herein relate to superconductor tapes and methods for
manufacturing, measuring, monitoring, and controlling same, which,
inter alia, achieve well-aligned nanocolumnar defects and thus a
high lift factor, which can result in superior critical current
performance of the tape in, for example, high magnetic fields.
BACKGROUND
[0004] Several materials systems are being developed to solve the
looming problems with energy generation, transmission, conversion,
storage, and use. Superconductors are quite likely a unique system
that provides a solution across a broad spectrum of energy
problems. Superconductors enable high efficiencies in generators,
power transmission cables, motors, transformers and energy storage.
Further, superconductors transcend applications beyond energy to
medicine, particle physics, communications, and transportation.
Superconducting tapes have come of age, enabled by a novel approach
to create epitaxial, single-crystal-like thin films on
polycrystalline substrates. In this technique, a thin film of
materials with rock-salt crystal structure such as MgO is deposited
by ion beam-assisted deposition over flexible, polycrystalline
substrates.
[0005] Superconducting films that are processed by this technique
exhibit critical current densities comparable to that achieved in
epitaxial films grown on single crystal substrates. Using this
technique, several institutions have demonstrated pilot-scale
manufacturing of superconducting composite tapes. It is quite
remarkable that currently a single crystal-like epitaxial film may
be manufactured to over a length of a kilometer using a
polycrystalline substrate base.
[0006] However, there are certain drawbacks to today's
superconductor tapes. The current carrying capability of
superconductors rapidly diminishes in a magnetic field, which poses
a problem for their use in applications such as wind generators
where the generator coil would be subjected to magnetic fields of a
few Tesla. Additionally, since superconductivity in
high-temperature superconductors (HTSs) is localized within their
Cu--O planes, HTS materials exhibit strong anisotropic behavior.
This anisotropy is evident in critical current measurements when a
magnetic field is aligned at different angles to the film surface
(FIG. 1A). As shown in FIG. 1A, the critical current of a standard
HTS tape drops rapidly as the field is moved away from the film
surface and reaches a low value when the field is oriented
perpendicular to the tape, which is the limiting value in coils
constructed with these tapes.
[0007] Pinning improvement strategies for practical superconductors
have been actively developed over the last decade to improve
in-field performance. The most explored approach has been to
introduce defects into the superconductor that are comparable in
lateral dimensions to superconducting coherence length. In 2G HTS
tapes, such defects include oxygen vacancies, threading
dislocations, twin planes, impurity atoms, irradiation-induced
columnar defects, and nanostructured inclusions of various
composition and structure.
[0008] Recently, to improve pinning, researchers developed an
approach for columnar defect formation based on chemically doping
the superconducting film with BaMO.sub.3 (M=Zr, Sn, Hf, Nb, Ce, Ta,
etc.). The BZO and BaSnO.sub.3 (BSO) inclusions form nano-sized
columns, about 5 nm in diameter, by a self-assembly process during
superconductor film growth and significantly improve the pinning
strength. FIG. 1B displays a cross sectional microstructure of a
(Gd,Y)Ba.sub.2Cu.sub.3O.sub.x (Gd--YBCO) superconducting film grown
by MOCVD with abundant self-assembled BaZrO.sub.3 (BZO)
nanocolumnar defects, mostly oriented perpendicular to the film
plane. Films with such a microstructure exhibit two-fold improved
performance in a magnetic field at 77 K, especially in orientations
along the direction of the BZO nanocolumns and result in a lower
anisotropy, as shown in FIG. 1A.
[0009] Furthermore, research demonstrated that a higher level of Zr
addition led to more favorable properties in magnetic fields at low
temperatures. In particular, the `lift factor,` which is the ratio
of critical current of the tape in applied magnetic field at low
temperature to the critical current of the tape at 77 K in zero
magnetic field, was found to be increased in tapes with higher
levels of Zr content. It was also recently shown that high critical
current density can be achieved in RE--Ba--Cu--O (REBCO, RE=rare
earth) tapes with high levels of Zr addition, even at 77 K. This
achievement opened the possibility of combining lift factor at low
temperatures in magnetic fields with high critical current density
at 77 K to reach very high critical currents at the low
temperatures in magnetic fields of interest to many applications.
However, it has since been discovered that REBCO tapes with high
levels of Zr addition do not always lead to high lift factors at
lower temperatures in magnetic fields. In essence, for REBCO tapes
with high levels of Zr addition, the lift factor at lower
temperatures in magnetic fields has been found to be inconsistent.
Accordingly, there is need in the art for superconducting tapes
that can consistently achieve substantially high critical currents
at lower temperatures in magnetic fields.
Summary
[0010] Embodiments are directed to a superconductor tape
comprising: a substrate; a buffer layer overlying the substrate;
and a superconductor film overlying the buffer layer. The
superconductor film is defined as having a c-axis lattice constant
higher than 11.74 Angstroms.
[0011] In an embodiment, the superconductor film (or the tape in
general) is over 10 meters in length.
[0012] In an embodiment, the superconductor film comprises 5 to 30
mol % of dopant selected from the group consisting of Zr, Sn, Ta,
Nb, Hf, Ce, and a combination thereof.
[0013] In an embodiment, the superconductor film comprises
BaMO.sub.3, where M=Zr, Sn, Ta, Nb, Hf, or Ce, and which has a
(101) peak of BaMO.sub.3 elongated along an axis that is between
60.degree. to 90.degree. from an axis of the (001) peaks of the
superconductor film.
[0014] Embodiments are also directed to a superconductor tape
comprising: a substrate; a buffer layer overlying the substrate;
and a superconductor film overlying the buffer layer. The
superconductor film comprises BaMO.sub.3, where M=Zr, Sn, Ta, Nb,
Hf, or Ce, and which has a (101) peak of BaMO.sub.3 elongated along
an axis that is between 60.degree. to 90.degree. from an axis of
the (001) peaks of the superconductor film.
[0015] In an embodiment, the (101) peak of BaMO.sub.3 is measured
by X-ray diffraction.
[0016] In an embodiment, the superconductor film (or the tape in
general) is over 10 meters in length.
[0017] In an embodiment, the superconductor film comprises 5 to 30
mol % of dopant selected from the group consisting of Zr, Sn, Ta,
Nb, Hf, Ce, and a combination thereof.
[0018] In an embodiment, the superconductor film is defined as
having a c-axis lattice constant higher than 11.74 Angstroms.
[0019] Embodiments are further directed to a superconductor tape
comprising: a substrate; a buffer layer overlying the substrate;
and a superconductor film overlying the buffer layer. The
superconductor film comprises BaMO.sub.3, where M=Zr, Sn, Ta, Nb,
Hf, or Ce, and which has a (101) peak of BaMO.sub.3 located at a
2theta angle higher than 30.degree. when measured by X-ray
Diffraction using copper k alpha radiation.
[0020] In an embodiment, the superconductor film comprises 5 to 30
mol % of dopant selected from the group consisting of Zr, Sn, Ta,
Nb, Hf, Ce, and a combination thereof.
[0021] In an embodiment, the superconductor film is defined as
having a c-axis lattice constant higher than 11.74 Angstroms.
[0022] Embodiments are yet further directed to a superconductor
tape comprising: a substrate; a buffer layer overlying the
substrate; and a superconductor film overlying the buffer layer.
The superconductor film comprises BaMO.sub.3, where M=Zr, Sn, Ta,
Nb, Hf, or Ce, and which has a (101) peak of BaMO.sub.3 located at
a 2theta angle less than 2.6.degree. from the (103) peak of the
superconductor phase when measured by X-ray Diffraction using
copper k alpha radiation.
[0023] In an embodiment, the superconductor film comprises 5 to 30
mol % of dopant selected from the group consisting of Zr, Sn, Ta,
Nb, Hf, Ce, and a combination thereof.
[0024] In an embodiment, the superconductor film is defined as
having a c-axis lattice constant higher than 11.74 Angstroms.
[0025] Embodiments are yet further directed to a method of
measuring a c-axis lattice parameter of a superconductor film in a
superconductor tape. The method comprises providing a
superconductor tape comprising: a substrate; a buffer layer
overlying the substrate; and a superconductor film deposited over
the buffer layer. The method also comprises measuring the c-axis
lattice parameter of the superconductor film via in-line X-ray
Diffraction in real-time during deposition of the superconductor
film over the buffer layer.
[0026] In an embodiment, the step of measuring is performed
subsequent deposition of the superconductor film.
[0027] In an embodiment, the superconductor film (or the tape in
general) is over 10 meters in length.
[0028] In an embodiment, the superconductor film comprises 5 to 30
mol % of dopant selected from the group consisting of Zr, Sn, Ta,
Nb, Hf, Ce, and a combination thereof.
[0029] In an embodiment, the c-axis lattice parameter is a c-axis
lattice constant higher than 11.74 Angstroms.
[0030] In an embodiment, the superconductor film comprises
BaMO.sub.3, where M=Zr, Sn, Ta, Nb, Hf, or Ce, and which has a
(101) peak of BaMO.sub.3 elongated along an axis that is between
60.degree. to 90.degree. from an axis of the (001) peaks of the
superconductor film.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The foregoing summary, as well as the following detailed
description, will be better understood when read in conjunction
with the appended drawings. For the purpose of illustration only,
there is shown in the drawings certain embodiments. It's
understood, however, that the inventive concepts disclosed herein
are not limited to the precise arrangements and instrumentalities
shown in the figures.
[0032] FIG. 1A is a plot illustrating anisotropy in critical
current of MOCVD-based HTS tape with and without self-assembled
BaZrO.sub.3 (BZO) nanocolumns.
[0033] FIG. 1B is a diagram illustrating cross-sectional
microstructures of a Zr-doped superconducting film synthesized by
MOCVD, showing abundant nanocolumnar defects of self-assembled
BZO.
[0034] FIG. 2A is a diagram illustrating a cross-sectional TEM
analysis of a Zr-added (Gd,Y)BCO tape with a low lift factor in
I.sub.c at 30 K, 2.5 T, showing not well-aligned, discontinuous BZO
nanocolumns perpendicular to the tape plane.
[0035] FIG. 2B is a diagram illustrating a cross-sectional TEM
analysis of a Zr-added (Gd,Y)BCO tape with a high lift factor in
I.sub.c at 30 K, 2.5 T, exhibiting strongly-aligned, continuous BZO
nanocolumns.
[0036] FIG. 3A is a plot illustrating (007) peaks of the REBCO
phase of several Zr-doped (Gd,Y)BCO tapes with increasing levels of
(Ba+Zr)/Cu content, as measured by X-ray Diffraction using copper
K-alpha (Cu K--.alpha.) radiation.
[0037] FIG. 3B is a table illustrating the (Ba+Zr)/Cu composition
of the REBCO tapes referenced in the plot of FIG. 3A.
[0038] FIG. 4 is a plot illustrating a c-axis lattice parameter of
several Zr-doped (Gd,Y)BCO tapes with increasing levels of
(Ba+Zr)/Cu content, as measured by X-ray Diffraction.
[0039] FIG. 5 is a plot illustrating dependence of the lift factor
in critical current at 30 K of several Zr-doped (Gd,Y)BCO tapes
with increasing values of c-axis lattice parameter, as measured by
X-ray Diffraction.
[0040] FIG. 6 is a plot illustrating (101) peaks of BZO of several
Zr-doped (Gd,Y)BCO tapes with increasing levels of (Ba+Zr)/Cu
content, as measured by X-ray Diffraction using Cu K--.alpha.
radiation.
[0041] FIG. 7 is a plot illustrating the angular distance between
the peak locations of the BZO (101) peak and (103) peak of the
REBCO phase of several Zr-doped (Gd,Y)BCO tapes with increasing
levels of (Ba+Zr)/Cu content, as measured by X-ray Diffraction
using Cu K--.alpha. radiation.
[0042] FIG. 8 is a plot illustrating the lift factor in critical
current at 30 K, 3 T with changing angular distance between the
peak locations of the BZO (101) peak and (103) peak of the REBCO
phase of several Zr-doped (Gd,Y)BCO tapes with increasing levels of
(Ba+Zr)/Cu content, as measured by X-ray Diffraction using Cu
K--.alpha. radiation.
[0043] FIG. 9A is a plot illustrating two-dimensional (2D) X-ray
Diffraction (XRD) data from Zr-added (Gd,Y)BCO tapes with
strongly-aligned, long BZO nanocolumns exhibiting a high lift
factor in critical current at 30 K, 3 T.
[0044] FIG. 9B is a plot illustrating two-dimensional (2D) XRD data
from Zr-added (Gd,Y)BCO tapes with not well-aligned, short BZO
nanocolumns exhibiting a low lift factor in critical current at 30
K, 3 T.
[0045] FIG. 10 is a perspective view of a schematic diagram
illustrating an in-line X-ray diffraction unit to measure the
c-axis lattice parameter as a superconductor tape is being
fabricated.
[0046] FIG. 11 is a plot illustrating shift of a (007) peak of
REBCO tapes with different (Ba+Zr)/Cu content from theta-2theta
scans using the in-line XRD tool using Cu K--.alpha. radiation.
[0047] FIG. 12 is a plot illustrating correlation between the
c-axis lattice constants of REBCO films with different (Ba+Zr)/Cu
content and the intensity of RE.sub.2O.sub.3 peaks of the films, as
measured by X-ray Diffraction using Cu K--.alpha. radiation.
[0048] FIG. 13 is a flowchart illustrating an embodiment of a
method of measuring a c-axis lattice parameter of a superconductor
film in a superconductor tape, in accordance with an
embodiment.
[0049] FIG. 14 is a perspective schematic and cross-sectional
diagram illustrating a microstructure of an ultra-thin film
high-temperature superconducting tape, in accordance with an
embodiment.
DETAILED DESCRIPTION
[0050] Heavy-doping of REBCO films is necessary, but not a
sufficient enough condition to achieve high lift factor in critical
current (I.sub.c) at low temperatures. The inventors have
discovered that a strong alignment of BaMO.sub.3 (M=Zr, Sn, Hf, Nb,
Ce, Ta, etc.) nanocolumns along the c-axis of the REBCO films is an
important condition to achieving high lift factors. For example,
FIGS. 2A and 2B show cross-sectional microstructures of two tapes
with the same J.sub.c of 3.08 MA/cm.sup.2 at 77 K, 0 T, but with
different lift factors in critical currents of 3.85 and 6.93 at 30
K, 2.5 T (B.parallel.c). The tape in FIG. 2A has a low lift factor,
and it consists of BZO nanocolumns that are not well-aligned and
not continuous from the buffer layers to the film surface. On the
other hand, the tape in FIG. 2B has a high lift factor and consists
of strongly-aligned BZO nanocolumns continuous from the buffer
layers to the film surface. The inventors have discovered that the
microstructural difference shown in FIG. 2A-2B is the culprit
behind the large scatter in the critical current of doped GdYBCO
tapes at 30 K, 3 T. Accordingly, along with the Zr-doping, a strong
alignment of BZO nanocolumns along the c-axis of the REBCO films is
critical to achieve consistently high lift factors. While the
embodiments described herein primarily reference BZO films, it is
understood that the embodiments equally apply to any BaMO.sub.3
(M=Zr, Sn, Hf, Nb, Ce, Ta, etc.) films.
[0051] However, microstructural examination of the alignment of
such nanocolumns in REBCO tapes is a destructive technique and is
relegated to very small areas of a few square micrometers. It is
therefore desirable to provide a nondestructive method that can be
used to examine larger areas of REBCO tapes to verify if the
highly-aligned nanocolumnar defects are present. Additionally,
there is great value if such method can be implemented in-line in
the processing of REBCO tapes so that the feedback from the
microstructural analysis can be used in real-time for monitoring
and, in turn, control of the process to achieve well-aligned
nanocolumnar defects and hence superior critical current
performance in high magnetic fields.
[0052] By detecting/measuring the BaMO.sub.3 (M=Zr, Sn, Hf, Nb, Ce,
Ta, etc.) nanocolumn alignment in real-time during superconductor
manufacture, the manufacturing process can be modified to
consistently obtain the required degree of alignment. Examples of
modification to the manufacturing process are lowering the
deposition temperature and/or increasing the oxygen partial
pressure and/or increasing the barium content in the precursor
and/or decreasing the copper content in the precursor. These and
other advantages of the present invention will become more fully
apparent from the detailed description of the invention herein
below.
[0053] It is to be understood that the figures and descriptions of
the present invention may have been simplified to illustrate
elements that are relevant for a clear understanding of the present
embodiments, while eliminating, for purposes of clarity, other
elements found in a typical superconductor tape or typical method
for fabricating, measuring, monitoring, or controlling a
superconductor tape. Those of ordinary skill in the art will
recognize that other elements may be desirable and/or required in
order to implement the present embodiments. However, because such
elements are well known in the art, and because they do not
facilitate a better understanding of the present embodiments, a
discussion of such elements is not provided herein. It is also to
be understood that the drawings included herewith only provide
diagrammatic representations of the presently preferred structures
of the present invention and that structures falling within the
scope of the present embodiments may include structures different
than those shown in the drawings. Reference will now be made to the
drawings wherein like structures are provided with like reference
designations.
[0054] Before explaining at least one embodiment in detail, it
should be understood that the concepts set forth herein are not
limited in their application to the construction details or
component arrangements set forth in the following description or
illustrated in the drawings. It should also be understood that the
phraseology and terminology employed herein are merely for
descriptive purposes and should not be considered limiting.
[0055] It should further be understood that any one of the
described features may be used separately or in combination with
other features. Other embodiments of devices, systems, methods,
features, and advantages described herein will be or become
apparent to one with skill in the art upon examining the drawings
and the detailed description herein. It's intended that all such
additional devices, systems, methods, features, and advantages be
protected by the accompanying claims.
[0056] For purposes of this disclosure, the terms "film" and
"layer" may be used interchangeably.
[0057] Embodiments of the present application are directed to a
non-destructive method to rapidly qualify the (Ba+Zr)/Cu content of
REBCO tapes, which may optionally be implemented even in real-time
during processing of the tapes as a quality control tool.
Additionally, embodiments of the present application provide a
non-destructive method to qualify the orientation of the
nanocolumnar defects of BaMO.sub.3, which determines the magnitude
of the lift factor in critical current performance. Therefore, at
least one objective of embodiments of the present application is to
consistently achieve a uniformly high critical current in a
magnetic field in long lengths of REBCO tapes. Another objective is
to develop a quality control (QC) tool to monitor the quality of
the REBCO tape in situ during tape fabrication (or after
fabrication) so as to enable uniformly high critical current in a
magnetic field. Moreover, a key aspect of embodiments of the
present application is the development of a non-destructive, rapid,
in-line quality control method that can be used to determine the
quality of the alignment of nanocolumnar defects and, in turn,
predict the performance of REBCO tapes in high magnetic fields.
[0058] In an embodiment, a nondestructive method based on X-ray
Diffraction (XRD) of superconductor tapes is capable of determining
the critical compositional ratio of Ba, Cu, and dopant on which the
critical current of the tape in a magnetic field depends on. In
another embodiment, an XRD method is disclosed that can
nondestructively determine the degree of orientation of
nanocolumnar defects in the superconductor film of superconductor
tape. In yet another embodiment, an X-ray Diffraction unit in an
in-line mode in a superconductor deposition apparatus can obtain
real-time information on the compositional ratio of Ba, Cu, and
dopant.
[0059] FIG. 3A, by way of example only, is a plot illustrating
(007) peaks of the REBCO phase of several Zr-doped (Gd,Y)BCO tapes
with increasing levels of (Ba+Zr)/Cu content, as measured by XRD
using Cu K--.alpha. radiation. In other words, FIG. 3A shows the
(007) peak from XRD analysis of Zr-added REBCO tapes with different
compositions of Ba, Cu, and Zr. FIG. 3B, by way of example only, is
a table illustrating the (Ba+Zr)/Cu composition of the REBCO tapes
referenced in the plot of FIG. 3A. As shown in FIGS. 3A-3B, as the
(Ba+Zr)/Cu content increases, the (007) peak location shifts to
2theta values, i.e., the c-axis lattice parameter increases. FIG.
4, by way of example only, is a plot illustrating a c-axis lattice
parameter of several Zr-doped (Gd,Y)BCO tapes with increasing
levels of (Ba+Zr)/Cu content, as measured by XRD. The
aforementioned trend of increasing c-axis lattice parameter with
increasing content of (Ba+Zr)/Cu in the REBCO tape is clearly shown
in FIG. 4. Specifically, as the (Ba+Zr)/Cu content in the REBCO
tape is increased from 0.53 to 0.84, the c-axis lattice parameter
increases from 11.72 .ANG. to 11.84 .ANG.. The c-axis lattice
parameter increases sharply beyond 11.74 .ANG.. FIG. 5, by way of
example only, is a plot illustrating the dependence of the lift
factor in critical current of several Zr-doped (Gd,Y)BCO tapes with
increasing values of c-axis lattice parameter, as measured by XRD.
As shown in FIG. 5, as the c-axis lattice parameter of the REBCO
tape increases, the lift factor in critical current at 30 K, 3 T
(magnetic field B.parallel.c-axis) also increases. Hence, the
measurement of the c-axis lattice parameter or the shift in the
2theta value of a (001) peak of REBCO by XRD is a very good
indicator of the in-field critical current performance of the
tape.
[0060] While a higher value of (Ba+Zr)/Cu and a higher c-axis
lattice parameter is desirable, it does not assure achieving good
in-field performance in REBCO tapes. As shown in FIG. 2B, it is
also essential that the BZO nanocolumns are well-aligned through
the thickness of the REBCO film. Since there is a tendency of the
BZO nanocolumns to orient along the a-b plane in heavily-doped
films, it is more challenging to assure the uninhibited growth of
c-axis-aligned nanocolumns. Minor fluctuations in the temperature,
oxygen partial pressure and incorporation of barium and copper in
the films can perturb the growth of well-aligned nanocolumns.
Additionally, it is important to achieve a well-aligned nanocolumn
growth without excessive (Ba+Zr)/Cu and too high a c-axis lattice
parameter of REBCO since the critical current at 77 K in zero
magnetic field may be reduced. To achieve a high critical current
at lower temperatures in high magnetic fields, it important to
achieve a high lift factor as well as good critical current at 77 K
in zero magnetic field.
[0061] FIG. 6, by way of example only, is a plot illustrating the
(101) peaks of the BZO phase of several Zr-doped (Gd,Y)BCO tapes
with increasing levels of (Ba+Zr)/Cu content, as measured by XRD
using Cu K--.alpha. radiation. As shown in FIG. 6, as the
(Ba+Zr)/Cu content increases, the (101) peak location of the BZO
phase shifts to higher 2theta values, i.e., its lattice parameter
increases. The (101) peak location of the BZO phase shifts to
values higher than 30.degree. for (Ba+Zr)/Cu content greater than
0.71.
[0062] FIG. 7, by way of example only, is a plot illustrating the
angular distance between the peak locations of the BZO (101) peak
and (103) peak of the REBCO phase of several Zr-doped (Gd,Y)BCO
tapes with increasing levels of (Ba+Zr)/Cu content, as measured by
XRD using Cu K--.alpha. radiation. As shown in FIG. 7, as the
(Ba+Zr)/Cu content increases beyond 0.72, the distance between the
peak locations of the BZO (101) peak and (103) peak of the REBCO
phase decreases below 2.6.degree.. In other words, as the
(Ba+Zr)/Cu content increases beyond a certain threshold, the
lattice parameters of BZO and REBCO phase become closer
together.
[0063] FIG. 8, by way of example only, is a plot illustrating the
lift factor in critical current at 30 K, 3 T with changing angular
distance between the peak locations of the BZO (101) peak and (103)
peak of the REBCO phase of several Zr-doped (Gd,Y)BCO tapes with
increasing levels of (Ba+Zr)/Cu content, as measured by XRD using
Cu K--.alpha. radiation. As shown in FIG. 8, as the angular
distance between the peak locations of the BZO (101) peak and (103)
peak of the REBCO phase decreases below 2.6.degree., the lift
factor in critical current at 30 K, 3 T increases to values of 6
and higher. As the lattice parameters of BZO and REBCO phase become
closer together, the BZO nanocolumns become better aligned leading
to higher lift factors in critical current.
[0064] FIG. 9A, by way of example only, is a plot illustrating 2D
XRD data from Zr-added (Gd,Y)BCO tapes with strongly-aligned, long
BZO nanocolumns exhibiting a high lift factor in critical current
at 30 K, 3 T. As shown in FIG. 9A, the BZO (101) peak in the REBCO
film with strongly c-axis-aligned BZO nanocolumns is found to
streak or elongate in a direction nearly perpendicular to the (001)
peaks of the REBCO phase. In general, the elongation of the BZO
(101) peak is along a direction that is between 60.degree. and
90.degree. from the axis of the (001) REBCO peaks. The REBCO (103)
peak itself is shifted towards smaller 2theta values and therefore
closer to the BZO (101) peak. These two features are not seen in
the Zr-added (Gd,Y)BCO tapes with not well-aligned BZO nancolumns
exhibiting a low lift factor in critical current at 30 K, 3 T, as
illustrated in FIG. 9B. The BZO (101) peak is elongated along a
constant 2theta arc, which is aligned at an angle less than
60.degree. from the axis of the (001) REBCO peaks.
[0065] FIG. 10, by way of example only, is a perspective view of a
schematic diagram illustrating an in-line X-ray diffraction (XRD)
unit/tool that can measure the c-axis lattice parameter as a
superconductor tape is being fabricated. With reference to FIG. 10,
in one embodiment, an XRD unit is placed in-line with a
superconductor deposition unit so as to measure, in real-time, any
shift in the c-axis lattice parameter of the REBCO phase in the
superconductor tape as it is being produced. If the c-axis lattice
parameter of the superconductor film is monitored during its
deposition, any deviation from the desired threshold value can be
determined and the process can be re-tuned. The XRD unit consists
of an X-ray source using a chromium anode as well as a line
(linear) or area (2D) X-ray detector that can instantaneously
measure the diffracted X-ray peaks over a 2.theta. range of 39-135
degrees. The X-ray source and detector are positioned so as to
detect the (007) peak of REBCO. As the tape exits the
superconductor deposition unit, it enters the XRD unit. The exact
2.theta. position of the (007) peak is obtained at different
locations along the length of the tape. By monitoring the magnitude
of the deviation of the (007) peak from the normal location, the
shift in the c-axis lattice parameter can be determined. By
continuously monitoring the shift in the (007) REBCO peak location,
the shift in the REBCO c-axis lattice parameter and hence the
(Ba+Zr)/Cu composition of the film can be determined over the tape
length. This real-time data of the REBCO film composition can then
be used to adjust the process parameters. For example, the tape
temperature, oxygen partial pressure and/or supply of barium and
copper precursors can be adjusted in real-time so as to achieve
consistent composition of (Ba+Zr)/Cu, and, consequently, consistent
critical current performance. These process parameters can be
adjusted to maintain the (Ba+Zr)/Cu composition is the optimum
interval so as to obtain a high lift factor in critical current as
well as good critical current at 77 K in zero applied magnetic
field. In another embodiment, the XRD unit can monitor shift in
other (001) peaks of REBCO for the same purposes.
[0066] FIG. 11, by way of example only, is a plot illustrating
shift of a (007) peak of REBCO tapes with different (Ba+Zr)/Cu
content from theta-2theta scans using the in-line XRD unit/tool
shown in FIG. 10. The disclosed in-line XRD tool can discern shifts
in the (007) peaks of REBCO films with significantly different
(Ba+Zr)/Cu content. As shown in FIG. 11, the 2.theta. location of
the (007) peak of the film shifts towards lower values of 2.theta.
(larger lattice parameter) in films with higher levels of
(Ba+Zr)/Cu content. In one embodiment, the 2.theta. angular
resolution of the in-line XRD tool can be improved by modifying the
linear detector-to-tape distance and the X-ray optics, such as the
number of sensors per units length of the linear detector, as
needed, so that subtle changes in (001) peak position can be
detected for slight changes in (Ba+Zr)/Cu composition in the REBCO
films.
[0067] In another embodiment, the X-ray source and linear detector
shown in FIG. 10 can be positioned such that the location of the
BMO (101) peak of the superconductor tape is monitored as it is
produced in the superconductor deposition unit. The exact 2.theta.
position of the BMO (101) peak is obtained at different locations
along the length of the tape. By monitoring the magnitude of the
deviation of the BMO (101) peak from the normal location, the shift
in the c-axis lattice parameter can be determined. By continuously
monitoring the shift in the BMO (101) peak location, the (Ba+Zr)/Cu
composition of the film can be determined over the tape length, as
per the data shown in FIG. 6. This real-time data of the REBCO film
composition may then be used to adjust the process parameters, such
as tape temperature, oxygen partial pressure and/or supply of
barium and copper precursors in real-time so as to achieve
consistent composition and, consequently, consistent critical
current performance.
[0068] In yet another embodiment, the X-ray source and linear
detector shown in FIG. 10 can be positioned such that the locations
of the BMO (101) peak and the REBCO (103) peak of the
superconductor tape are monitored as the tape is produced in the
superconductor deposition unit. The exact 2 .theta. positions of
the BMO (101) peak and the REBCO (103) peak can be obtained at
different locations along the length of the tape. By continuously
monitoring the magnitude of the difference in the 2.theta.
positions of the BMO (101) peak and the REBCO (103) peak, the
(Ba+Zr)/Cu composition of the film can be determined over the tape
length, as per the data shown in FIG. 7. This real-time data of the
REBCO film composition can then be used to adjust the process
parameters such as tape temperature, oxygen partial pressure and/or
supply of barium and copper precursors in real-time so as to
achieve consistent composition and, consequently, consistent
critical current performance.
[0069] In yet another embodiment, the linear detector shown in FIG.
10 is replaced with an area two-dimensional (2D) detector. In this
case, the BMO (101) peak may tilt away from its 2.theta. arc and
towards the REBCO (103) peak, as illustrated in FIG. 9A,
continuously as the superconductor tape is produced in the
superconductor deposition unit. The angle of the tilt of the BMO
(101) peak from the axis of the REBCO (001) peaks, as illustrated
in FIG. 9A, may also be measured continuously. The manufacturing
process parameters, such as tape temperature, oxygen partial
pressure and/or supply of barium and copper precursors, may then be
adjusted in real-time so as to achieve a tilt of the BMO (101) peak
within an angle between 60.degree. and 90.degree. from the axis of
the REBCO (001) peaks. By this method, a consistent growth of
well-aligned BMO nanocolumns may be achieved and, consequently, a
consistent critical current performance may also be achieved.
[0070] FIG. 12, by way of example only, is a plot illustrating the
correlation between the c-axis lattice constants of REBCO films
with different (Ba+Zr)/Cu content, and the intensity of the
RE.sub.2O.sub.3 peaks of the films, as measured by XRD. In addition
to monitoring the 2theta peak location of the (001) peak, the
in-line XRD tool can also be utilized to monitor the peak intensity
of the RE.sub.2O.sub.3 peaks along the length of the tape. FIG. 12
shows the correlation between the RE.sub.2O.sub.3 peak intensity of
tapes with different c-axis lattice constants of the REBCO film.
REBCO films with higher c-axis lattice constants show reduced
RE.sub.2O.sub.3 peak intensity. Hence, by monitoring the
RE.sub.2O.sub.3 peak intensity with in-line XRD in the processing
of REBCO tapes, one can determine changes in the (Ba+Zr)/Cu content
in the tapes.
[0071] FIG. 14, by way of example only, is a perspective schematic
and cross-sectional diagram illustrating a microstructure of an
ultra-thin film high-temperature superconductor tape, in accordance
with an embodiment. The superconductor tape 1400 comprises: a
substrate 1410; a buffer layer 1420 overlying the substrate 1410;
and a superconductor film 1430 overlying the buffer layer 1420. In
one embodiment, the superconductor film of FIG. 14 is defined as
having a c-axis lattice constant higher than approximately 11.74
Angstroms. In one embodiment, the superconductor film (or the tape
in general) is over 10 meters in length. In another embodiment, the
superconductor film comprises 5 to 30 mol % of dopant selected from
the group consisting of Zr, Sn, Ta, Nb, Hf, Ce, or a combination
thereof. In still another embodiment, the superconductor film
comprises BaMO.sub.3, where M=Zr, Sn, Ta, Nb, Hf, or Ce, and which
has a (101) peak of BaMO.sub.3 elongated along an axis that is
between 60.degree. to 90.degree. from an axis of the (001) peaks of
the REBCO superconductor film.
[0072] In another embodiment, the superconductor film 1430 of FIG.
14 may comprise BaMO.sub.3, where M=Zr, Sn, Ta, Nb, Hf, or Ce, and
which has a (101) peak of BaMO.sub.3 elongated along an axis that
is between 60.degree. to 90.degree. from an axis of the (001) peaks
of the REBCO superconductor film. In one embodiment, the (101) peak
of BaMO.sub.3 is measured by XRD. In another embodiment, the
superconductor film (or the tape in general) is over 10 meters in
length. In yet another embodiment, the superconductor film
comprises 5 to 30 mol % of dopant selected from the group
consisting of Zr, Sn, Ta, Nb, Hf, Ce, and a combination thereof. In
still another embodiment, the superconductor film is defined as
having a c-axis lattice constant higher than 11.74 Angstroms.
[0073] In yet another embodiment, the superconductor film 1430 of
FIG. 14 may comprise BaMO.sub.3, where M=Zr, Sn, Ta, Nb, Hf, or Ce,
and which has a (101) peak of BaMO.sub.3 located at a 2theta angle
higher than 30.degree. when measured by X-ray Diffraction using
copper k-alpha radiation. In an embodiment, the superconductor film
comprises 5 to 30 mol % of dopant selected from the group
consisting of Zr, Sn, Ta, Nb, Hf, Ce, and a combination thereof. In
another embodiment, the superconductor film is defined as having a
c-axis lattice constant higher than 11.74 Angstroms.
[0074] In still another embodiment, the superconductor film 1430 of
FIG. 14 may comprise BaMO.sub.3, where M=Zr, Sn, Ta, Nb, Hf, or Ce,
and which has a (101) peak of BaMO.sub.3 located at a 2theta angle
less than 2.6.degree. from the (103) peak of the superconductor
phase when measured by XRD using copper k-alpha radiation. In an
embodiment, the superconductor film comprises 5 to 30 mol % of
dopant selected from the group consisting of Zr, Sn, Ta, Nb, Hf,
Ce, and a combination thereof. In another embodiment, the
superconductor film is defined as having a c-axis lattice constant
higher than 11.74 Angstroms.
[0075] By way of example only, FIG. 13 is a flowchart of a method
1300 of measuring a c-axis lattice parameter of a superconductor
film in a superconductor tape. In an embodiment, a superconductor
tape comprising a substrate, buffer layer, and superconductor film
may be provided (block 1302). The buffer layer overlies the
substrate, and the superconductor film is deposited over the buffer
layer. A c-axis lattice parameter of the superconductor film is
measured in real-time via in-line X-ray Diffraction (block 1304)
during deposition of the superconductor film over the buffer layer.
In one embodiment, the measuring step 1304 is performed subsequent
to deposition of the superconductor film. In an embodiment, the
superconductor film (or the tape in general) is over 10 meters in
length. In yet another embodiment, the superconductor film
comprises 5 to 30 mol % of dopant selected from the group
consisting of Zr, Sn, Ta, Nb, Hf, Ce, and a combination thereof. In
another embodiment, the c-axis lattice parameter is a c-axis
lattice constant higher than 11.74 Angstroms. In an embodiment, the
superconductor film comprises BaMO.sub.3, where M=Zr, Sn, Ta, Nb,
Hf, or Ce, and which has a (101) peak of BaMO.sub.3 elongated along
an axis that is between 60.degree. to 90.degree. from an axis of
the (001) peaks of the REBCO superconductor film, or which has a
(101) peak of BaMO.sub.3 located at a 2theta angle less than
2.6.degree. from the (103) peak of the superconductor phase when
measured by XRD using copper k-alpha radiation.
[0076] It is understood that the superconducting film discussed in
connection with FIG. 14 and FIG. 13 can include one or more of the
features discussed above in connection with those figures. Features
in any of the embodiments described above may be employed in
combination with features in other embodiments described above, and
such combinations are considered to be within the spirit and scope
of the present invention. Moreover, although the embodiments in
method 1300 and the structure of the superconductor tapes are
described above with reference to various layers, additional layers
may alternatively be implemented in the method 1300 as well as the
structure of the superconductor tapes described in any of the
embodiments above. Furthermore, the method steps in any of the
embodiments described herein are not restricted to being performed
in any particular order. Such alternatives are considered to be
within the spirit and scope of the present invention, and may
therefore utilize the advantages of the configurations and
embodiments described above. The contemplated modifications and
variations specifically mentioned above are considered to be within
the spirit and scope of the present invention.
[0077] It's understood that the above description is intended to be
illustrative, and not restrictive. The material has been presented
to enable any person skilled in the art to make and use the
concepts described herein, and is provided in the context of
particular embodiments, variations of which will be readily
apparent to those skilled in the art (e.g., some of the disclosed
embodiments may be used in combination with each other). Many other
embodiments will be apparent to those of skill in the art upon
reviewing the above description. The scope of the embodiments
herein therefore should be determined with reference to the
appended claims, along with the full scope of equivalents to which
such claims are entitled. In the appended claims, the terms
"including" and "in which" are used as the plain-English
equivalents of the respective terms "comprising" and "wherein."
* * * * *